Importance of β,β-carotene 15,15'-monooxygenase 1 (BCMO1) and β,β-carotene 9',10'-dioxygenase 2 (BCDO2) in nutrition and health

Mol Nutr Food Res. 2012 Feb;56(2):241-50. doi: 10.1002/mnfr.201100387. Epub 2011 Dec 7.


In humans, varying amounts of absorbed β-carotene are oxidatively cleaved by the enzyme β,β-carotene 15,15'-monooxygenase 1 (BCMO1) into two molecules of all-trans-retinal. The other carotenoid cleavage enzyme β,β-carotene 9',10'-dioxygenase (BCDO2) cleaves β-carotene at the 9',10' double bond forming β-apo-10'-carotenal and β-ionone. Although the contribution of BCDO2 to vitamin A formation has long been debated, BCMO1 is currently considered the key enzyme for retinoid metabolism. Furthermore, BCMO1 has limited enzyme activity towards carotenoids other than provitamin A carotenoids, whereas BCDO2 exhibits a broader specificity. Both enzymes are located at different sites within the cell, with BCMO1 being a cytosolic protein and BCDO2 being located in the mitochondria. Expression of BCMO1 in tissues other than the intestine has recently revealed its function for tissue-specific retinoid metabolism with importance in embryogenesis and lipid metabolism. On the other hand, biological activity of BCDO2 metabolites has been shown to be important in protecting against carotenoid-induced mitochondrial dysfunction. Single-nucleotide polymorphisms (SNPs) such as R267S and A379V in BCMO1 can partly explain inter-individual variations observed in carotenoid metabolism. Advancing knowledge about the physiological role of these two enzymes will contribute to understanding the importance of carotenoids in health and disease.

Publication types

  • Review

MeSH terms

  • Animals
  • Carotenoids / metabolism*
  • Cytosol / metabolism
  • Dioxygenases
  • Fatty Acid Desaturases / physiology*
  • Genetic Variation
  • Humans
  • Mitochondria / metabolism
  • Nutritional Physiological Phenomena
  • Organ Specificity
  • Polymorphism, Single Nucleotide
  • Retinoids / metabolism
  • Substrate Specificity
  • beta-Carotene 15,15'-Monooxygenase / physiology*


  • Retinoids
  • Carotenoids
  • Dioxygenases
  • Fatty Acid Desaturases
  • BCO2 protein, human
  • BCO1 protein, human
  • beta-Carotene 15,15'-Monooxygenase